Variable displacement fluid pump or motor



y 21, 1959 HI. GOLD ETAL 2, 9

VARIABLE DISPLACEMENT FLUID PUMP OR MOTOR Filed June 2, 1955 2 Sheets-Shee t 1 2% /8 s A y f gm I 5 u: 3;; J z// I 1522212 0.275 MAOAD c2010 3 I 4 ii iig" July 21, 1959 V H. GOLD ETAL 2,895,422 7 VARIABLE DISPLACEMENT FLUID PUMP OR MOTOR Filed June 2. 1955 2 Shets-Sheet 2 Wigs- United States Patent O VARIABLE DISPLACEMENT FLUID PUMP. OR MOTOR Harold Gold and David M. Straight, Shaker Heights, Ohio Application June 2, 1955, Serial No. 512,608

3 Claims. (Cl. 103-120) This invention relates generallyto positive fluid displacement means such as pumps or motors and more particularly relates to a positive displacement type pump of the type utilizing rotary gears as the rotary fluid displacement means, the pump including relatively movable housing parts and means for adjusting the parts to selectively vary the spacing dimension between the axes of rotation of the gears, thereby to vary the meshing overlap of the gears and selectively changing the discharge characteristics of the pump.

It is an object of the present invention to provide a gear pump whereby improved means are utilized to eifect variations in volumetric displacement.

Another object of the present invention is to provide a variable displacement pump which retains the basic simplicity of a fixed displacement pump.

"Yet another object of the present invention is to provide a variable displacement pump which may be used as a motor without alteration of physical structure.

Many other advantages, features, and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings in which a preferred structural embodiment of a variable displacement fluid pump or motor incorporating the principles of the present invention is shown by way of illustrative example.

On the drawings:

Figure l is a cross sectional view of a pump embodying the principles of the present inventiontaken substantially on line 11 of Figure 3 and illustratingthe components of the pump in position of adjustment Figure 3 is a cross sectional view of parts shown in elevation taken substantially on line 3-3 of Figure 1.

Figure 4 is a cross sectional view taken substantially on line.44 of Fim lre 5 showing an alternative embodiment of a pump. incorporating the principles of the .present invention.

Figure 5 is a cross sectional view. of parts shown in elevation taken substantially on line 5-5 of Figure 4 and showing additional details of construction of. the pump of Figure 4.

Figure 6 is a cross sectional view of an additionalembodiment of a pump incorporating the. principles of the present invention taken substantially on line 6.-.-6. of Figure 7.

Figure 7 is a cross sectional view of, parts shown in elevation taken substantially on line 77 of Figure 6.

As shown on the drawings:

Referring first of all to Figures 1, 2 and 3, there is shown a pump indicated generally by the reference numeral 10 comprising rotary fluid displacement means which take the form of a pair of rotary gears 11 and 12 having spaced parallel axes of rotation and each "having .the housing part 16 a bore 19 forming a pumping chamber for the gear 11.

Adjacent the pumping chamber 19 and on one side thereof is provided a reduced bore 20, the bore walls of which provide a bearing surface for journaling and supporting the end of a shaft 21 connected to the gear 11.

Adjacent the pumping chamber 19 on the other side is 'a reduced bore 22, the bore Walls of which form additional bearing means for journaling and supporting the shaft 21 connected to the gear 11.

The housing of the pump 10 includes a second housing part 23 which is also characterized by the formation therein of a bore 24 providing a pumping chamber for 'the gear 12. The bores 19 and 24 of the respective housing parts 16 and 23 cooperate with one another to form a unitary pumping cavity in which the gears 11 and 12 are rotated in meshing overlap relation, thereby 'to move fluid from the inlet 17 to the outlet 18.

The first housing part 16 is particularly characterized by the formation thereon of an offset body portion indicated at 26. The body portion 26 has formed therein a generally rectangular recess identified by the reference number 27 and including oppositely disposed spaced apart pairs of side Walls, one pair of side Walls being indicated at 28 and the other pair of side walls being indicated at 29.

The second housing part 23 has an overall outward configuration which is generally complementary to the shape of the recess 27 and includes side wall portions which slidably engage and abut against corresponding adjacent walls 29, 28 of the first housing part 16. It will be manifest, therefore, that the walls 29, 28 of the first housing part 16 and the corresponding adjacent side walls of the second housing part 23 cooperate to form guideways which prescribe and confine the limits of relative movement between the housing parts. 16 and 23.

More specifically, the guideways formed by the walls 29, 28 prescribe a track which is in oflset parallel relation to a plane passing through the rotational axis of the shaft 21.

Referring further to the second housing part 23, it will be noted that adjacent the pumping chamber 24 and on opposite sides thereof, there is provided reduced bores 30, the bore walls of which form bearing means for journaling and supporting a shaft 31 connected to the gear 12. Thus, the rotational axis of the shaft 31 is also in spaced parallel relation to the rotational axis of the shaft 21.

Upon elfecting relative movement between the housing parts 16 and 23, the respective axes of the shafts 21 and 31 and hence of the gears 11 and 12 are relatively moved in parallel planes. By virtue of such adjustment, the spacing dimension between the shafts21'and 31 may be selectively varied. When such spacing dimension is varied, the meshing overlap relation of the gears is likewise varied. This. characteristic is clearly illustrated in comparing Figures 1 and 2, Fig. 1 showing the gears in full meshing overlap relation and Fig. 2 showing the housing parts 16 and 23. adjusted to vary the meshing overlap relation of the gears 11 and 12.

In operation, it will be appreciated that a small running clearance exists between the peripheral tips of the gear teeth 13 and the bore walls of the pumping. chambers 19 and 24. Similarly, a small running clearance exists between the side walls of the pumping chambers 19 and. 24 and the adjoining side faces of the gears 11 and 12.2 The gears 11 and 12 are thereby free to rotate but form an AA BA essentially fluid tight seal with the walls of the respective ment of the housing part 23 relative to the housing part 16 along the mating plane 32 causes a change in the perpendicular distance between the axes of the shaft. In

Fig. l, the-housing part 23 is shown in such a position that the perpendicular distance between the shaft axes is approximately the shortest that permits free running of the gears 11 and 12 In Fig. 2, the housing parts are shown in such a position that the perpendicular distance between the shaft axes has been increased.

When the spacing dimension between the axes of rotation between the gears 11 and 12 is increased in accordance with the principles of the present invention and as illustrated in Figures 1 and 2, the gears 11 and .12 maintain a co-axial relation with respect to the respective pumping chambers 19 and 24 and also maintain the essentially fluid tight contact with the bore walls of these chambers. In the position such as illustrated in Fig. 2, however, even though the gears 11 and 12 maintain intermeshing contact, the gear teeth 13 do not mutually fill the tooth spaces 14 as completely as in the fully meshed position illustrated in Fig. 1. Because of this characteristic, a portion of the volume of fluid carried by the outer tooth spaces is returned by the inner tooth spaces. Accordingly, the net volume of fluid transported from the inlet 17 to the outlet 13 in a complete revolution of the pump gears 11 and 12 is reduced as the perpendicular distanceor spacing dimension between the gear axes is increased.

The net volume of fluid transported through the pump 10 in a complete revolution of the gears 11 and 12 approaches zero as the line of contact of the gear teeth approaches the ends or tips of the teeth 13. As the line of contact of the intermeshing gear teeth moves toward the ends of the teeth, the torque developed by the gear in pumping against a given head of fluid reduces and approaches zero as the line of contact approaches the ends of the teeth. Thus, the pump of the present invention is a true variable displacement pump since a constant rotational speed may be maintained and with a constant pressure rise, the power absorbed by pump reduces as the volumetric flow through the pump is reduced. a

In order to lock the housing part 16 and 23 in various positions of adjustment, there is shown a threaded aperture 33 in the housing part 16 at the body portion 26 receiving a locking screw 34. It will be understood that the locking screw 34 is turned into locking engagement with the movable housing part 23 to maintain the parts in any selected adjustment position.

In Fig. 4 an alternative embodiment of a pump construction is illustrated wherein the shaft axes are adjusted in a common plane. In this form of the invention, the pump is indicated at 10a and comprises a first housing part 36 having formed therein a bore providing a pumping chamber 37 for a first gear 38. A shaft 39 for the gear 38 is journaled by the first housing part 36 at a bearing surface 40 formed by a reduced bore adjacent the pumping chamber 37.

The first housing part 36 has an inlet 41 and an outlet 42 at opposite sides of pumping chamber 37. A recess 43 is also provided in the first housing part 36 and includes a reduced portion 44 which is located on one side of the rotational axis of the shaft 39, an enlarged recess portion 46 being located on the opposite side of the shaft axes of the shaft 39.

Received in the recess 43 is a second housing part 47 having an enlarged portion 48 formed with a bore providing a pumping chamber 49 in which a second gear 50 is rotated. A shaft 51 for the gear 50 is journaled at a bearing surface 52 for-med by a reduced bore in the second housing part 47 adjacent the pumping chamber 49.

A reduced portion 53 is provided on a second housing part 47 and is complementary in shape and received by the reduced recess portion 44 of the recess 43.

The side walls of the first housing part 36 and the adjacent side walls of the second housing part 47 slidably engage one another and form guideways for prescribing and confining the relative movement of the parts in such a manner that the axes of the shafts 51 and 39 will be adjusted through a common plane and variation of the perpendicular distance between the gear axes may thus be obtained. Any selected adjustment of the housing parts is locked by means of a lock screw 54 received in a corresponding threaded aperture 56 provided by the first housing part 36, the lock screw 54 engaging the second housing part 47.

In Figures 6 and 7, there is illustrated yet another embodiment of a pump incorporating the principles of the present invention. 7

In this form of the invention, the pump 10b has housing 57 formed with an inlet 65, an outlet 75 and a pumping chamber which includes at its opposite ends a pair of bore portions 58 and 59. The housing 57 encloses, however, a bracket or housing member 60 which is rotatably or angularly adjustable, a shaft portion 61 extending outwardly of the housing 57 for angularly adjusting the bracket or housing member 60 on a predetermined axis of angular adjustment.

As is clearly indicated in Fig. 6, the bracket or housing member 60 includes a curved wall portion 62 which forms a part of the pumping chamber 59 in the housing 57 and further includes parallel spaced apart leg portions 63 each having a reduced bore 64 providing a bearing surface for receiving and journaling opposite ends of a shaft 66 connected to a gear 67. The reduced bores 64 are offset thereby to provide an offset axis of rotation for the gear 67 with respect to the axis of adjustment of the bracket or housing member 60. The driver gear of the pump 10b is indicated at 68 and has a shaft 69 journaled at one end in a bearing surface provided by a reduced bore 70 formed adjacent the pumping chamber 58 and journaled by a second bearing surface 71 on the other side of pumping chamber 58.

Upon angularly adjusting the bracket or housing member 60, the perpendicular spacing dimension between the shafts 66 and 69 will be selectively varied.

Since the bracket or housing member 60 has cylindrical projections 72 extending from the sides of pumping chamber 59 which are arranged in parallel relation to the axis of the shaft 66 but eccentrically offset with respect to such axis, angular adjustment of the bracket or housmg member 60 will change the positioning of the axis of the shaft 66. Throughout such an adjustment, however, the crescent shaped curved wall 62 of the pumping chamber 59 provides an essentially fluid tight seal with the tips of the gear teeth and movement of the axis of the shaft through an arc, the radius of which being equal to the fixed perpendicular distance between the axis of the shaft 66 and the shaft 61 will be effected.

Although various minor modifications might be suggested by those versed in the art, it should be understood that we wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of our contribution to the art.

We claim as our invention:

1. A pump comprising first and second housing parts and having guideways slidably connecting said housing parts to one another for relative movement, said housmg parts having confronting wall portions particularly characterized by the formation therein of a pumping chamber in each said housing part disposed on axes in spaced parallel relation and each pumping chamber opening into the corresponding portions of said confronting Wall surfaces, thereby to form together with one another a generally figure S-shaped pumping cavity for a pair of meshing gears, one of said housing parts having an inlet and an outlet formed therein to conduct fluid to and away from said pumping cavity, a rotary gear journaled in each said housing part for rotation on a corresponding one of said axes, said gears being in mesh with one another at said confronting surfaces of said housing parts, said rotary gears having a maximum meshing overlap with one another when said parts are aligned with a line connecting said axes in substantially a right angular relationship with said confronting surfaces, and manually operated locking means operatively connected between said parts and accessible from the outside of the pump to lock said housing parts at difierent positions of adjustment with said line connecting said axes disposed at different angles relative to said confronting surfaces, thereby to adjust the meshing overlap of the gears and vary the displacement of the pump.

2. A pump comprising a housing having adjoining movable parts complementally shaped to form together with one another intersecting bores providing a pumping cavity and having an inlet and an outlet, rotary intermeshing gear fluid displacement means in said pumping cavity for moving fluid from said inlet to said outlet, bearing means in said housing journaling said rotary gear fluid displacement means and establishing separate spaced apart axes of rotation in respective adjoining housing parts, adjustment means for selectively positioning said housing parts to vary the spacing dimension -between said axes, thereby varying the delivery of said pump, said adjustment means including locking means accessible from the outside of the pump to lock the housing parts with said axes at selected different positions of adjustment, said housing parts having adjoining relatively movable surfaces on a mating plane parallel to said axes of rotation confining said parts and the corresponding rotary gear fluid displacement means for relative movement of said axes in parallel planes and including confronting surfaces recessed to open into said pumping cavities.

3. In a gear pump, a pair of rotary gears having spaced parallel axes of rotation and circumferentially spaced peripheral teeth in meshing overlap relation, a first housing part having an inlet and an outlet and a bore formed therein providing a pumping chamber between the inlet and outlet and receiving one of said gears, said first housing part having reduced bores formed on opposite sides of said pumping chamber, a shaft for one of said gears journaled in said reduced bores, said first housing part having walls forming an enlarged recess adjacent said pumping chamber, a movable second housing part slidably mounted in said recess and having a bore formed therein providing a pumping chamber receiving the other of said gears, and reduced bores formed on opposite sides of said pumping chamber, a shaft for said other gear journaled in said reduced bores of said second housing part, said first and second housing parts having slidably engageable wall portions forming guideways confining said parts for relative movement to vary the spacing dimension of said shaft and confronting recessed wall portions opening into the respective pumping chambers, and locking means between said parts to lock said parts in selected positions of adjustment to vary the displacement of the pump by adjusting the meshing overlap of the gears at said confronting recessed wall portions.

References Cited in the file of this patent UNITED STATES PATENTS 1,602,740 Bechler Oct. 12, 1926 1,691,713 Frey Nov. 13, 1928 1,704,704 Grant Mar. 12, 1929 1,897,560 Lawser Feb. 14, 1933 2,754,765 Joy July 17, 1956 FOREIGN PATENTS 263,590 Great Britain Jan. 6, 192.7 

